Does anyone know how to test an abs brake sensor on a 2005 1.6tdci focus cmax, without firstly having to go to a garage. What could be the most obvious cause for the abs light staying on? All help appreciated

One of your wheel sensors are defective. Have a mechanic troubleshoot it. You can still drive without the ABS. Your regular brakes will still work.

By "were done" I am guessing someone else did the job for you. It is a common error at garages to forget to reconnect the sensors so that is my first thought but then you say you changed the front sensors, was that after the brake job and do you have 4 wheel ABS? The plugs for the sensors should always be cleaned if not replaced after a brake job in my opinion (high dirt area). More info will get you a better answer if you post back I may be able to help more/better.

Finding the fault code will not clear the problem if you reset the system without finding the cause the light will just come on again or the fault code will not clear.
Anything related to brakes should be checked out by a garage/mechanic and not ignored.
Its probably just an abs sensor failed but its better to be safe than sorry.
Sorry for the lecture but I wouldnt like to see anyone hurt due to brake system failure.

Hi Graham
check your brake fluid first
remove each wheel and check your sender ring and your sensor wire and connection
if they are ok trace the sensor wires back in case there is a junction before the abs block
if that is ok
get it tested at a garage for a report and replace the parts required per the report

When the abs light comes on it is telling you that there is a fault in the abs system. If it comes on and stays on when you start the car it is almost always a speed sensor issue. If it comes on when you start the car but then comes on after you start driving it could still be a speed sensor or in rare occasions a broken tone ring but it usually has other symptoms associated with a broken tone ring, You best option is to have the abs system scanned for trouble codes. This will narrow down the hundreds of possibilities and give yo a definite path to focus on. If you shave a vollt meter you could start by checking the speed sensors. The first thing you can do is ohm all of the sensors. There will be one at each wheel and they should ohm out about the same. If one is not the same as the others than reaching that sensor would be a good start. If they ohm out o.k. Than you get set your meter to a/c voltage and check to see what the pipit of the speed sensors are with the wheels moving. That should give you a couple of things to check into. Let me know if you have any questions.

I’m happy to assist further over the phone at https://www.6ya.com/expert/jeremy_d728a59f986299fa

there should be

when does this grinding sound occour ?

You have a faulty abs censor.Have a diagnostic check done to see which one is at fault.Good luck.

Really the best thing you can do is unplug one of the abs sensor wires by the front wheel and get it fix when you can..Really like they said you dont need them but they should have unhooked it for you because sometimes them things will engage when you dont want them to and that could get you in a wreck..But by unplugging the sensor it will by-pass the abs and it wont do that any moe.It will stop when you want to stop.But when it is slippery out side you know not to lock up the brakes..If you lock them up in slippery condition you will slide of the road..But if you know how to pump the brakes you'll have no problem slipping around..But other than that you really dont need them..thats really the only timee they really kick in is when its sliding.If you find someone later that will work on it cheap thats great..But dont forget to unplug that wire..That will stop that scarey feeling you get when you try to stop..Hope this helps you and have a great night!!!!!!!

I’m happy to assist further over the phone at https://www.6ya.com/expert/joe_a3369546f8067589

Ok the reason I ask is that will help to pinpoint the concern. See ABS system when you first turn the ignition on will do a self test on itself,light turns on for a few seconds then turns off if everything proves out. Then when you start driving once you reach about 12 mph it will activate the pump and perform a 2nd self test.If everything is ok light stays off,if it see's a problem it turns on the light and disables the ABS.
Since yours comes on after you start driving then problem is most likely a wheel speed sensor concern. Since you just did a rear brake job and the problem started after this I would say it is one of the rear sensors.You need to look at the sensors and make sure the sensor and ring look ok and that you didn't get grease or dirt in the teeth of the sensor ring or maybe bent the end of one of the sensors and make the gap larger between sensor and ring.